Heterogeneous catalytic epoxidation of olefin over a hydrothermally synthesized 3D phosphate bridged copper(II) framework

Abstract

A 3D copper phosphate, [Cu₂(PO₄)(OH)] _n (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction analysis. In [Cu₂(PO₄)(OH)] _n , there are two types of copper centers having distorted trigonal bipyramidal geometry and distorted octahedral geometry that are connected by the μ₂-bridging of each phosphate oxygen ultimately forming a η⁸-PO₄ bridged 3D network. The compound exhibited excellent catalytic performance in olefin epoxidation. Epoxidation of styrene and substituted styrenes, as well as bulky olefins like cycloalkenes and long-chain alkenes, is efficiently catalyzed by [Cu₂(PO₄)(OH)] _n using tert-butylhydroperoxide in acetonitrile. The results obtained in the heterogeneous catalytic reactions show that the olefins are converted to the respective epoxides in good yield with high selectivity. [Cu₂(PO₄)(OH)] _n was catalytically more active and selective in comparison to simple copper(II) phosphate salt in heterogeneous medium. The catalyst can be recycled and reused several times without significant loss of activity.

Keywords:

• Metal-inorganic framework
• Copper(II) phosphate
• Heterogeneous catalysis
• tert-Butylhydroperoxide
• Olefin epoxidation

Acknowledgment

We acknowledge DST for funding the Department of Chemistry, Jadavpur University to procure single crystal XRD machine under DST-FIST programme.